A pallet changer is installed in front of a machine tool such as a vertical machining center. A plurality of pallets are located on a pallet stand of the pallet changer and hydraulic cylinders are fixed to the pallet stand. One hydraulic cylinder is provided for each pallet.
For example, when transferring the first pallet to the table, the table is moved to the position opposite to the first pallet. And, the first rod of the first hydraulic cylinder is expanded so that the first pallet engaging the first rod is transferred to the table. After the first rod is contracted, a work on the first table is machined. Next, the first rod is expanded to engage the first pallet. The first rod is then contracted so that the first pallet is returned to the pallet stand.
To transfer the second pallet, the table is moved to the position opposite to the second pallet. And, the second rod of the second hydraulic cylinder is expanded so that the second pallet engaging the second rod is transferred to the table. After the second rod is contracted, a work on the second table is machined. Next the second rod is expanded to engage the second pallet. The second rod is then contracted so that the second pallet is returned to the pallet stand.
With a pallet changer of this type, large hydraulic cylinders are used. Moreover, the number of hydraulic cylinders needed is equal to the number of pallets, consequently the pallet changer is heavy and large in size and expensive to make. Moreover, when the hydraulic cylinder starts or stops, the pallet and the work are shocked at its stroke end. The pallets can not be transferred in smooth manner.